I-deficiency is endemic in cattle and sheep in
Ireland. The prevalence of low I-status in unsupplemented animals at
pasture is >80%. The body recycles I poorly. In supplemented animals in
I-deficient groups, PII falls within 5-15 days of removal of I-supplement.

Confirmation of low I status: A blood test
for plasma inorganic I (PII) is the most reliable way to confirm a low I-status in a problem group.
Ideally one should test 10 animals individually. Low to very low I-status is
confirmed if the group mean PII is <50 ug/L, or >50% of the group are
<45 ug/L. Plasma T3 and/or T4
tests are unreliable in assessing I status. Bulk milk I tests
are unreliable unless they arelow - "normal" milk I values may arise in I-deficient
herds if iodine-based disinfectants contaminate the bulk tank.

Non-clinical I-deficiency is common: Most
low I-status animals are clinically healthy; they show no signs of
I-deficiency, or apparent depression of health or productivity. I-supplementation
of such animals usually does not improve their health, productivity or
profitability.

Daily target for I-supplementation: The
target suggested for I-supplementation is 10 mg I/100 kg LW/d, or about
60 mg I/d for cows, 6 mg I/d for ewes. Pro rata supplements are suggested for
other ruminants. As long as the animals get this level of I-supplement during
the critical times of the year, it does not matter whether the supplement is
given in the feed, on the feed, or via the water supply.

Breeding animals: Critical times for I
supplementation are late pregnancy (especially in the last month), at peak
lactation and before/during the breeding season, until pregnancy is
confirmed by veterinary examination (rectal or ultrasound). In herds with non-infectious
abortions, I-supplement may be needed throughout pregnancy

Young and growing animals: Signs of
I-deficiency include low immunity to infection, low growth rate, poor coats.
Similar signs may be due to other factors (inadequate quality/ quantity of feed,
parasitism, chronic infections, other mineral deficiencies etc. Differential
diagnosis is important. Young and growing animals may need I-supplements if
they show signs of I-deficiency and if blood tests show low PII.

A. IODISED FEEDS OR MINERAL MIXTURES

Assuming that cows need a supplement of 60 mg
I/d, one must assess their supplements on two criteria: (a) the level
of supplementary feeding (kg/cow/d) and (b) the level of I in the
supplement (mg/kg). In all cases, (a) X (b) must = 60. For example, iodised
concentrates, to be fed at 8 to 0.5 kg/cow/d, or mineral mixtures to be fed at
150, 125 or 100 g/cow/d (0.150, 0.125 or 0.100 kg/cow/d), must contain the
following I-levels:

Iodised Winter
Concentrates for Cows (8-4 kg)

Iodised Summer
Feeds for Cows (3.0-0.5 kg)

Iodised Mineral
Mixtures for Cows (150-100 g)

Feeding rate
(kg/cow/d)

8

7

6

5

4

3

2

1

0.5

.150

.125

.100

Daily
I-input (g/cow/d)

60

60

60

60

60

60

60

60

60

60

60

60

I-level
(mg/kg)

7.5

8.6

10

12

15

20

30

60

120

400

480

600

Assuming that ewes need a supplement of 6
mg I/d in a concentrate allowance of 2 to 0.25 kg/ewe/d, or in iodised mineral
mixes fed at 30 to 15 g/ewe/d (0.030 to 0.015 kg/ewe/d), a similar table for ewes is:

Iodised
Concentrates for Ewes

Iodised Mineral
Mixtures for Ewes

Feeding rate
(kg/ewe/d)

2.0

1.5

1.0

0.5

0.25

.030

.025

.020

.015

Daily
I-input (g/ewe/d)

6

6

6

6

6

6

6

6

6

I-level
(mg/kg)

3

4

6

12

24

200

240

300

400

.

B. 4% KI-MIXTURE AS A SIMPLE
I-SUPPLEMENT

If animals need an I-supplement (and other
I-supplements are not being provided), trough water can be medicated by 4%
potassium iodide (KI) mixture cheaply and effectively. Vets or pharmacists can make a 4% KI-mixture
in bulk for use as an I-supplement in I-deficient animals:

KI-MIXTURE: Contains 40 mg KI (= 30
mg I)/ml. POISON. For animal treatment only. Keep away from
children. For use as an I-supplement for animals. Use ONLY in ANIMALS
and ONLY as DIRECTED.

USAGE OF KI-MIXTURE: I-deficient
animals need I-supplements at frequent and regular intervals during the
times of greatest risk.

DOSE :

Species

Type

ml/head/d

Cattle

Cows 600
kg

2.00

Stores
300 kg

1.00

Calves
100 kg

0.33

Sheep

Ewes

0.20

Store
lambs

0.14

Lambs at
weaning

0.07

Horses

Mares

0.67

Adult
horses

0.67

Yearlings

0.33

Foals 6
month-old

0.18

.

DO NOT EXCEED THE DOSE, EXCEPT ON
VETERINARY ADVICE

Do not use together with other high-I
sources (such as high-I mineral mixes, compound feeds supplying high
I etc). Alternatively, if animals are getting only part of their daily I
target from other sources, reduce the KI-dose accordingly to make up the
deficit. For example, if cows are getting 20 mg I/d from
another source and the target dose is 60 mg I/d, top up by giving
another 40 mg I (1.33 ml of 4% KI-mixture)/d.

SHAKE CONTAINER well before removing the
daily group dose. Trace-element mixtures may precipitate on storage.
Failure to shake the container frequently during use may cause
sedimentation. The upper layer of the mixture may contain low levels of
trace-elements and the lower layer may contain toxic levels. Animals
dosed from the upper layer may get too little supplement. Those dosed
from the lower layer can die of acute poisoning within a few days.

METHODS OF GIVING THE 4% KI-MIXTURE

The KI-mixture can be given to animals: (a)
individually, daily via water/milk/feed containers, or (b) to groups,
daily via the trough water, or (c) to groups, daily via the feed
(silage / hay / concentrate), or (d) individually, by drench at intervals of
2-3 weeks.

a. 4% KI-MIXTURE VIA INDIVIDUAL
WATER/MILK/FEED BOWLS

If animals (horses, veal calves etc) are watered
or fed individually, the KI-mixture can be added once/d to the feed
or drinking container.

Check the daily dose for each animal,
according to the stated dose rates. For example, a mare would get 1
ml/d; a veal calf (50 kg) would get 0.33 ml/d.

SHAKE CONTAINER well before removing the
daily dose.

Remove the daily dose into a 1 ml
syringe.

Add the daily dose (once/d) to the
feed or drinking bowl/bucket.

b. 4% KI-MIXTURE VIA THE WATER SUPPLY

If there is a controlled trough-water supply,
and the animals have no other source of drinking water (streams, ponds etc),
it is most convenient to add this mixture to the trough water for prophylactic
medication of I-deficient groups of animals.

Note: Young lambs and calves (especially
those suckling their dams) may drink little or no water. Hence, this method of
I-supplementation may not be relied upon in those animals.

Remove the daily dose for the group
into a
calibrated flask or container.

Split the dose over the day: If the whole dose is added once/d to small troughs, the early
drinkers may take too much, leaving too little for the others.
Therefore, add 50% of the daily group dose twice/d ( or, preferably,
33.3% three times/d) to the trough
water. On the
last addition of each day, rinse the calibrated container in the trough
water to ensure that no sediment remains in the calibrated container.

Stir the water in the trough
thoroughly after each addition of KI-mixture.

.

c. 4% KI-MIXTURE VIA THE FEED
(SILAGE/HAY/CONCENTRATE)

If animals are fed forage (silage or hay) or
concentrate, it is convenient to squirt this mixture evenly over the forage for
prophylactic medication of I-deficient groups.

Calculate and remove the total daily dose
for the group, as in (b 1, 2 and 3) above.

Spray 50% of the day's dose over the
feed on two occasions daily, in a fine jet from syringe and
fine needle, or a suitable spray-gun (such as a "Windowlele"
or "Dettol" spray-dispenser).

.

d. 4% KI-MIXTURE BY DRENCH AT INTERVALS OF 2-3
WEEKS

Drenching at intervals of 2-3 weeks may be the
only realistic option if methods (a to c) above are impractical, for example in
suckler calves, or in flocks of sheep. In that case, suggested doses for
drenching are:

DOSE (ml/head) for use at intervals of 2 or 3
weeks:

Species

Type

ml/head every 2 weeks

ml/head every 3 weeks

Cattle

Cows 600
kg

28.0

42.0

Stores
300 kg

14.0

21.0

Calves
100 kg

4.6

7.0

Sheep

Ewes

2.8

4.2

Store
lambs

2.0

2.9

Lambs at
weaning

1.0

1.5

Horses

Mares

9.3

14.0

Adult
horses

9.3

14.0

Yearlings

4.7

7.0

Foals 6
month-old

2.3

3.5

.

DO NOT EXCEED THE DOSE, EXCEPT ON
VETERINARY ADVICE

See the warnings in previous sections

Avoid dosing-gun injuries and avoid
dosing into the trachea

HORSES need less iodine (mg/kg body
weight) than ruminants. In particular, avoid the use of excessive
I-supplement in mares in late pregnancy, or young foals. Toxic goitre can
arise if those animals ingest excessive amounts. I supplements for mares
in late pregnancy should not exceed 30 mg/d.

C. AQUADYNE TABLETS VIA TROUGH WATER

Mayo
Healthcare (Westport)supplies
Aquadyne
"slow-release" tablets (420 mg I/tablet). To medicate the trough
water for a herd of cattle, the dose (D) of tablets is calculated as
follows:

Estimate the total liveweight of the cattle
to be dosed (TLW, in kg).

Decide on the dosing interval (DI, in
days). DI should be every 1 to 7 days, say twice/week, or at
an interval of 3.5 days.

Add fresh tablets at the predetermined dose
interval to the simple dispenser (supplied by the company). Immerse the
dispenser in the water trough. Remove the spent tablets, as needed, from the
opposite end of the dispenser.

D. IONOX BOLUSES FOR CATTLE

These are slow-release ruminal boluses, made by
Animax UK, and distributed by Bayer (UK and Ireland). They contain I, Co and
Se. An oral dose of 2-3 boluses/cow would provide sufficient I, Co and Se to
protect herds which would otherwise be severely deficient in those minerals for
a period of 5-7 months. In my opinion, the main role for slow-release
bolus-technology is in beef cows, beef cattle, or young dairy-replacements at
pasture, when water medication, or provision of carrier feeds high in
trace-element supplements may not be a practical option.